| Biodiversity is facing threats from climate change,and many wild animals are having to adapt to global warming by selecting new habitats.Rana hanluica is endemic to China,because of its important edible value,it has been illegally captured on a large scale,leading to the decline of the wild population.At present,the studies on Rana hanluica only exist in the aspects of morphology,biological habit and artificial farming,and the study on habitat selection is still blank.And it is still DD(Data Deficient)in the IUCN Red List of Threatened Species.In order to evaluate the survival status of Rana hanluica population,understand the habitat selection during the breeding period,predict the potential distribution area of Rana hanluica in China and the change of suitable habitat area under climate change in the future,the maximum entropy(MaxEnt)niche model and geographical information system(ArcGIS)were used to identify suitable habitat area under climate change scenarios in China(2050s&2070s).Based on the 47 effective distribution sites and 20 typical environmental factors of Rana hanluica in China,the suitable habitat model of Rana hanluica under modern and future climate conditions was established,and the related environmental impact factors were analyzed.At the same time,based on 13 habitat factors such as vegetation type,land use type,slope,slope direction and water temperature,the habitat selection of Rana hanluica during breeding period was studied in Yangmingshan National Nature Reserve,the habitat selection mechanism of Rana hanluica was explored.Rana hanluica was studied in terms of macro-geographical distribution and micro-habitat selection,with a view to providing a theoretical basis and reference for the conservation of the field population.The main results of this study are as follows:(1)Habitat characteristics by Rana hanluica during its breeding periodIn the breeding period,Rana hanluica prefer to choose the middle slope(hillside)and lower slope(valley bottom)with relatively gentle terrain(slope<30°),and choose the semi-shady and semi-sunny slope.The relative humidity of the surface environment is high(42-95%),and the average humidity reaches 77.86%.The surface temperature is high(10.8-28.7℃),with an average temperature of 22.3℃.Vegetation types are mainly crops(rice)and shrubs.The water depth is relatively shallow(average 6.183cm),the water temperature is relatively high(average 18.746℃),the oxygen content of the water is between 2.04 and 17.99mg/L,and the pH of the water is between 4.61 and 9.3.In addition,Rana hanluica tend to spawning in places far away from roads and settlements.(2)Habitat preference by Rana hanluica during its breeding periodThe types of ecological factors preferred by Rana hanluica were as follows:type of landscape selected for slope less than 15°(P=0.3077),slope position downhill(P=0.2941),the semi-shady and semi-sunny slope(P=0.0204);type of land use as paddy field(P=0.5663),surface moisture above 50%(P(50-80%)=0.2500;P(>80%)=0.1111),surface temperature between 10 and 20℃(P=0.3043);vegetation type was crops(e.g.rice,etc.)(P=0.1724);water conditions were water depth less than 10cm(P<5cm=0.1111;P5-10cm=0.2000),water temperature less than 20℃(P=0.3239),oxygen content between 3 and 6mg/L(P=0.2653)and 5.5<pH<8.5(P=0.4783);in addition,Rana hanluica preferred habitats more than 100 m from the nearest road(P=0.2000)and more than 200 m from the nearest settlement(P=0.0400).(3)The main factors affecting habitat selection of Rana hanluicaThe principal component analysis showed that the main factors influencing the habitat selection of the Rana hanluica were:slope,slope position,slope direction,land use type,temperature,water depth,water body pH,water body oxygen content;which can be defined into three categories:geographical factor,temperature factor and water body factor.Based on the absolute magnitude of the loadings,it is clear that the factors influencing habitat selection for Rana hanluica are,firstly,the geotechnical factor,followed by the water body factor and the temperature factor.(4)Evaluation of the potential geographical suitability of Rana hanluicaBased on MaxEnt model,the prediction accuracy of potential distribution area of Rana hanluica is very high,and AUC(receiver operating curve)values for the training and test sets of the model respectively are 0.993 and 0.994;the area of potentially suitable habitat for Rana hanluica under modern climatic conditions is 36.36×104 km2,and the potential geographical distribution area is mainly located in Hunan and Guizhou;the main environmental factors affecting the potential geographical distribution are the driest monthly precipitation,followed by the wettest seasonal precipitation and the coefficient of variation of precipitation.This indicates that these environmental factors contain important information.Overall,the main influencing factors are the precipitation variables(driest monthly precipitation,wettest seasonal precipitation and coefficient of variation of precipitation).When the probability of the presence of Rana hanluica population is greater than 0.5,the suitable range for the driest monthly precipitation is 30.88mm-133.1mm,the altitude range is 373.31m-1839.34m,the suitable range for the driest season mean temperature is-4.87℃-8.19℃,and the suitable range for isothermality is 15.59-28.37℃.(5)Prediction of the distribution area of Rana hanluica under future climate changeUnder the future climate scenario(2050 and 2070)with two representative concentration pathways(RCPs,SSP1-2.5&SSP5-8.5),The suitable habitat of Rana hanluica was reduced to different degrees,resulting in a decreasing trend of the total suitable habitat area.Under the SSP 1-2.6 emission scenario,the area of high suitability habitat for Rana hanluica in 2050 and 2070 is 0.11×104 km2 and 0.73×104 km2,a decrease of 98.5%and 86.1%respectively compared to the area of high suitability habitat for Rana hanluica under modern climatic conditions.Under the SSP5-8.5 emission scenario,the area of high suitability habitat for Rana hanluica in 2050 and 2070 is 0.34×104 km2 and 0.001×104 km2,a decrease of 95.3%and nearly 100%compared to the area of high suitability habitat for Rana hanluica under modern climatic conditions.Similarly,the area of medium suitable habitat for Rana hanluica also shows a decreasing trend under future climate change scenarios.Under the future SSP1-2.6 and SSP5-8.5 emission conditions,the latitude of the habitat of Rana hanluica tends to increase;under the SSP5-8.5 scenario,a more pronounced movement distance can be found,and its core distribution area is still dominated by Hunan Province.In conclusion,this study reveals that the main factors affecting habitat selection of Rana hanluica during the breeding period are the combined effects of geographical factors,water factors and temperature factors.Under the future climate change,the suitable habitat of Rana hanluica will be further reduced,mainly due to the influence of rainfall factors.It aims to help the relevant forestry departments to protect wildlife resources more effectively and to provide basic scientific information and reference for the protection of species diversity and ecological environment in China. |
